1. Field of the Invention
The present invention relates to the use of polymers based on ethylene, (meth)acrylates, and (meth)acrylic acid for coating or sealing panes of laminated safety glass. The invention also relates to aqueous emulsions of these polymers and also to a process for coating or sealing panes of laminated safety glass using these aqueous emulsions. The invention also relates to panes of laminated safety glass coated or sealed according to the invention.
2. Description of the Background
Panes of laminated safety glass, which are particularly significant for motorcars, are usually composed of two layers of silicate glass, between which a layer of plastics material is interposed. For this purpose other layers of optically effective materials may be used which filter out ultraviolet or infrared rays. The said layer of plastics material serves on the one hand to hold the two panes of silicate glass together, whilst on the other hand it is intended to hold the splinters together when there is breakage of the entire pane.
High demands are placed on the mechanical, thermal, and chemical resistance properties of this layer of plastics material. The polyvinylbutyral films usually still used today for this purpose satisfy these requirements to an inadequate extent. In particular, when moisture and aggressive contaminants from the air penetrate into this layer of plastics material this loses its colorless-transparent appearance and becomes turbid.
In the case of completely enclosed panes of laminated safety glass such as motor vehicle windscreens help is possible here by all-round sealing to a certain extent, but, for example, in the case of those motorcar side windows which allow such edge-sealing in very special circumstances only, hermetic sealing of the internal layer of plastics material has hitherto been very difficult to achieve.
Edge-sealing of motorcar side windows can only be carried out using a colorless-transparent seal, this being undetectable to a person viewing it. Commonly used colored, ie mostly dark to black sealing compositions, as used, eg, for motor vehicle windscreens, are unsuitable in such cases.
Is is thus an object of the present invention to provide a material which is suitable for coating panes of laminated safety glass and satisfies the necessary demands concerning mechanical, thermal, and chemical resistance. This material should also be suitable for colorless-transparent edge-sealing of such panes.
DE-A 2,136,076 (1) reveals copolymers of ethylene, vinyl acetate, 2-ethylhexyl acrylate, and methacrylic acid which are prepared by high-pressure polymerization. These copolymers are suitable for combining two panes of glass to produce vehicle windscreens. For this purpose, they are applied to the glass as molten film or as a solution.
U.S. Pat. No. 4,130,667 (2) describes copolymers of .alpha.-olefins such as ethylene and unsaturated carboxylic acids such as (meth)acrylic acid which may contain polymerized units of a third monomer component such as an unsaturated carboxylate, eg, 2-ethylhexyl (meth)acrylate. These copolymers are suitable for coating glass surfaces, eg, glass bottles. The copolymer is rolled on to the glass surface in powder form and then heated in order to produce the protective coating described.